The Present Application relates to a connector. In particular, the Present Application relates to an electrical connector for electrically connecting a board to a board.
An electrical connector such as a board-to-board connector has been hitherto known, which electrically connects boards arranged in parallel to each other or perpendicularly to each other. The board-to-board connector is provided with a pair of connectors which are attached to both of the boards to be connected. The respective connectors are electrically connected to the respective boards. One board and the other board are electrically connected to each other by the electric connection brought about between the connectors. The electrical connection between the boards and the connectors and the electrical connection between the connectors are performed by a plurality of contacts or contact terminals (connector terminals) which are provided on the respective connectors. The board and the connector are electrically connected to each other by soldering the contact terminals to the board. The connectors are electrically connected to each other by the elastic contact brought about between the contact terminals soldered to the respective boards. As disclosed in Japanese Patent Application No. 09-180829, the fitting or mating between the connectors is retained by the elastic contact brought about between the contact terminals described above.
Grooves and through-holes, which are used to attach the contact terminals, are formed for a housing of the connector. The housing of the connector is molded, for example, by the injection molding with an insulative material such as synthetic resin or the like.
When the housing, in which the through-holes are formed, is molded by the injection molding, weld lines appear in the vicinity of the through-holes. The weld line is a thin line allowed to appear at a portion at which the flows of the melted resin merge into one in the mold to cause the welding or fusion during the injection molding. The weld line has a weak strength as compared with surrounding portions, and it is feared that any crack or the like may arise. The melted resin, which is injected into the mold, is gradually cooled, and the viscosity thereof is raised. Therefore, the parts of melted resin, which merge into one, are not sufficiently dissolved with each other at the merging portion of the flows. The parts of melted resin are solidified while causing the phase separation. This portion causes the weld line.
The flow of the rein in the mold will be explained with reference to FIG. 13 in relation to the case in which the housing of the connector formed with the through-holes is injection-molded. A receptacle connector 800 has a box-shaped housing 811. The housing 811 has a pair of lateral walls 812a, 812b which extend in parallel to each other, a pair of longitudinal walls 826a (only one of them is shown) which connect both end portions of the lateral walls 812a, 812b to each other, and a bottom plate 817. The bottom plate 817 extends to connect the pair of lateral walls 812a, 812b and the pair of longitudinal walls 826a. A plurality of through-holes 818, into which contact terminals 861 are forcibly inserted or pressed-in as described later on, are formed in one array along the lateral wall 812a through the bottom plate 817. Protrusions 819a, which are formed to interpose the pressed-in contact terminals 861 from the both sides, are provided between the plurality of through-holes 818 so that the protrusions 819a extend in the height direction of the lateral wall 812a. 
When the housing 811 having the structure as described above is injection-molded, pins are arranged at portions corresponding to the through-holes 818 in the mold to prevent the inflow of the melted resin. A gate (not shown), from which the melted resin is introduced into the mold of the housing 811, is provided at a portion disposed in the upper-right direction in FIG. 13. The melted resin, which is injected into the mold, is allowed to flow in the direction directed from the right to the left of the housing 811 as viewed in FIG. 13. In this situation, the flow of the melted resin is once branched due to the presence of the pins, in the vicinity of the through-holes 818 at which the pins are arranged. The branched flows travel around the pins, and they merge into one again. The weld lines 830 appear at the merging portions of the resin. The weld lines arise in the vicinity of the through-holes 818 irrelevant to the position of the gate for introducing the melted resin, because the weld lines appear at the merging portions of the melted resin in the injection molding.
Further, as shown in FIG. 14, when the contact terminals 861 are pressed-in or forcibly inserted into the through-holes 818, the weld lines are stripped off upwardly due to the stress of the press-in. The enlarged or expanded weld lines become cracks 831. On the other hand, the high-function resin, which is excellent in the chemical resistance and the heat resistance, is used for the housing of the electrical connector. However, the molding is relatively difficult with the high-function resin, and the weld lines tend to appear with ease. For example, the liquid crystal resin (LCP) is excellent in the chemical resistance and the heat resistance. However, the liquid crystal resin (LCP) has the high orientation, and the melted resin of LCP is solidified in a short period of time. Therefore, the weld lines tend to appear with ease.